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Imagine being a microbiologist living in Japan in the early 1900s fresh into the new century hustling in your little lab and working on fungi from steamed rice. You grind and grind and extract, mix, boil, and steam until one day you come up with this weird new acid. You don’t know what it is and you don’t know what to do with it. Because of how daunting the process is, you don’t want to go through it again and you just forget about the compound and move on. A couple of years later, some hot shot takes a look at your notes, replicates your process, and finds a fancy name for it: kojic acid. He analyses it further and points out its structure and capabilities, including its use in cosmetics for hyperpigmentation and skin discolorations, and starts boasting about the discovery for attention at parties.
This is -roughly- the story behind kojic acid. It was first discovered by Dr. Saito in 1907. Today, Dr. Saito is cited as the person who discovered kojic acid. But that’s it. During my research on this skincare ingredient, I haven’t even been able to get his full name! For all I know, he could be a woman!
If only Saito hustled today. He’d kept things to himself, find a way to stabilize and formulate that acid into sustainable, refillable packaging, send out some samples to influencers, and bam! We could be slathering our faces with brightening moisturizers by Saito Beauty.
The moral of the story is don’t give up and let others feast on your hard work. All joking aside, there’s drama attached to this skin-brightening ingredient. And I’m sorry but I couldn’t move past that and dive straight to the point. But now that you know who to thank for this acid, we can move on.
You’ll find below everything, or everything else, you need to know about kojic acid in skincare, how it works, and how it benefits your skin.
What is Kojic Acid in Skincare?
Kojic acid is a compound derived from various types of fungi and a byproduct of fermented foods such as rice (1). The acid was named ‘kojic’ because ‘koji’ means steamed rice in Japanese, which is a reference to Dr. Saito’s discovery process where he isolated the acid from steamed rice.
In skincare, kojic acid works mainly as a skin lightening agent in the treatment of skin discoloration disorders like hyperpigmentation and melasma (2).
It’s formulated into skin care products to treat hyperpigmentation in concentrations ranging between 1% and 5%. And it’s commonly found in brightening serums, creams lotions, and gels.
How Does Kojic Acid Work For Hyperpigmentation?
Hyperpigmentation causes dark spots and patches to appear on the skin, giving you uneven skin tone. So how does kojic help with hyperpigmentation, then? Kojic acid works by inhibiting tyrosine activity (3). Tyrosine is the enzyme responsible for producing melanin, which is what pigments your skin. In doing so, kojic acid treats and prevents hyperpigmentation.
Let’s take a step back for a second and put things into perspective. Kojic acid is only one of the many skincare ingredients for hyperpigmentation. Other common skin brighteners include vitamin C, azelaic acid, niacinamide, tranexamic acid, and hydroquinone.
Among these ingredients, hydroquinone is considered to be the gold standard treatment for hyperpigmentation. On the flip side, it’s widely known for being very irritating to the skin, which makes its use very limited. So kojic acid is considered to be a gentler alternative to hydroquinone.
What Are The Skin Benefits of Kojic Acid?
The most important benefit of kojic acid for your skin is its ability to fade dark spots and treat hyperpigmentation (4). Whether you’re dealing with UV-induced dark spots, melasma, or post-inflammatory hyperpigmentation, kojic acid is an overall effective skin brightener that fades discolorations. Again, because it’s helpful with brightening dark spots from sun damage, it’s considered an anti-aging ingredient too.
Kojic acid is gentler on the skin compared to hydroquinone. That’s why it’s considered an alternative to hydroquinone. Moreover, kojic acid also has stabilizing effects. So it’s also used together with hydroquinone for better results too.
Kojic acid presents anti-bacterial effects too. It helps reduce acne caused by bacteria. And when you think about it, this is a great win for people with acne. You target both blemishes and discolorations from blemishes at the same time.
In addition, kojic acid also possesses anti-inflammatory and antioxidant effects. It’s not like the more potent antioxidants we have in our arsenal such as vitamin C. But it does have UV protective benefits for the skin.
In sum, kojic acid is excellent as a treatment ingredient for hyperpigmentation but also has these secondary benefits too.
What Are The Side Effects?
The most common drawback associated with using kojic acid in your skincare is irritation, especially when you have sensitive skin. Kojic acid can cause redness and sensitivity.
And according to the research, these side effects are more common when kojic acid is used in concentrations above 1% (5). But most over-the-counter kojic acid skin care products are usually made with 1%.
And also, there are esters of kojic acid too, which tend to be gentler on the skin. In sum, patch test if you have sensitive skin. Go ahead and do it anyway even if you don’t have sensitive skin.
But I’d like to point out something else here. Didn’t we say that kojic acid is gentler? Then why does it irritate? Well, apparently, kojic acid was tested frequently against hydroquinone and not necessarily other brighteners.
And when you compare something with hydroquinone, the other party usually ends up being gentler. This means that while kojic acid is a great alternative for anyone who’s had it with hydroquinone, it still carries the potential for irritation for the rest of us.
What Do Dermatologists Think About Kojic Acid?
It’s one thing when you use a certain ingredient in your skincare or you do your research. But things might change a bit when it comes to the daily practical use of these ingredients.
For that reason, I referred to two of my favorite dermatologists from around the world whose articles and videos I find genuinely helpful. I know you’ll recognize them too. So here’s what dermatologists think about kojic acid.
Dr. Alexis Stephens is a board-certified dermatologist and the founder of Parkland Dermatology & Cosmetic Surgery in Florida, U.S.A. She says that while kojic acid can help get rid of hyperpigmentation, it can also cause irritation. She suggests patch testing, starting slow, and using no more than 1%-2% (6).
Dr. Davin Lim is an award-winning, lead dermatologist in Cutis Dermatology in Brisbane, Australia. He says he likes to use kojic acid for pigmentation, and even for freckles because apparently, it helps with freckles a little bit too (7).
As you can gather, there’s not really a gap between what they say about kojic acid in literature and what practicing dermatologists think about it. I say that’s a win for us!
How To Use Kojic Acid in Skincare?
In light of all this information, you can already infer that you should start slowly with kojic acid. You can go for a kojic acid serum or cream or opt for a multi-tasker formulated with several other brighteners.
Use your product a few times a week at first until you have a pretty clear understanding of how your skin reacts to it. If things are looking good, you can use kojic acid daily.
Additionally, when you’re trying to treat hyperpigmentation, don’t underestimate the power of sun protection. Remember to use sunscreen daily and reapply every 2 hours.
So this is what kojic acid is, and how it works. Obviously, the reason why it is gaining attention is that it’s an effective ingredient in reducing hyperpigmentation. So if discolorations are getting you down, Dr. Saito’s got your back! And if you’re ready to see what’s out there, check out the best kojic acid products on the market.
Kojic Acid FAQs
- Brtko, J., Rondahl, L., Ficková, M., Hudecová, D., Eybl, V., & Uher, M. (2004). Kojic acid and its derivatives: history and present state of art. Central European journal of public health, 12 Suppl, S16–S18.
- Zachary, C. M., Wang, J. V., & Saedi, N. (2020). Kojic Acid for Melasma: Popular Ingredient in Skincare Products. Skinmed, 18(5), 271–273.
- Lajis, A. F., Hamid, M., & Ariff, A. B. (2012). Depigmenting effect of Kojic acid esters in hyperpigmented B16F1 melanoma cells. Journal of biomedicine & biotechnology, 2012, 952452. https://doi.org/10.1155/2012/952452
- Phasha V, Senabe J, Ndzotoyi P, Okole B, Fouche G, Chuturgoon A. Review on the Use of Kojic Acid—A Skin-Lightening Ingredient. Cosmetics. 2022; 9(3):64. https://doi.org/10.3390/cosmetics9030064
- Saeedi, M., Eslamifar, M., & Khezri, K. (2019). Kojic acid applications in cosmetic and pharmaceutical preparations. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, 110, 582–593. https://doi.org/10.1016/j.biopha.2018.12.006
- BEST Actives for Hyperpigmentation? (2020, October 11). [Video]. YouTube. https://www.youtube.com/watch?v=FM2RklSngz4
- 5 SKINCARE ACIDS | How to use, recommended brands, explained by dermatologist. (2020, May 4). [Video]. YouTube. https://www.youtube.com/watch?v=0fLxv6HKrPk